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Primary and Noncontributory Insurance Explained

By SubCover HQ · Updated Oct 29, 2026 · 2 min read

Almost every construction subcontract and many vendor agreements say the sub's liability insurance must be "primary and noncontributory" to the additional insureds. It's one of those phrases everyone copies into contracts and few people check. Here's what it means and how to verify it.

The problem it solves

When a sub's work causes an injury or damage on your project, the claim often lands on more than one policy: the sub's liability policy (where you're an additional insured) and your own liability policy. Without clear wording, the insurers can argue about who pays first and how to split the bill. Your policy may end up contributing, which can mean a claim on your loss history, a deductible, and higher premiums at renewal.

What the two words mean

• Primary: the sub's policy responds first for claims covered under the additional insured endorsement, before your own policy.
• Noncontributory: the sub's insurer won't ask your insurer to share (contribute to) the loss that the sub's policy covers.

Together, they're meant to keep claims arising from the sub's work on the sub's policy, which is usually what the contract intended in the first place.

Where it comes from

A standard general liability policy's "other insurance" clause doesn't automatically make it primary and noncontributory for an additional insured. The wording usually has to be added by endorsement. Insurers use standard forms such as ISO's primary and noncontributory endorsement (CG 20 01), or their own versions, and some blanket additional insured endorsements build the language in. The exact form varies by insurer, so the endorsement is what to ask for.

How it shows up on a certificate

The ACORD 25 has no checkbox for primary and noncontributory. Agents typically mention it in the Description of Operations box, for example: "Additional insured on a primary and noncontributory basis when required by written contract." That note is helpful, but like everything else on a certificate, it doesn't change the policy. The certificate says right at the top that it confers no rights. See how to read an ACORD 25 for more on that disclaimer.

How to verify it

1. Put the requirement in writing in your subcontract or vendor agreement. Many endorsements apply only "when required by written contract."
2. Request a copy of the endorsement that provides it, along with the additional insured endorsement.
3. Check that it applies to the right coverage. It's most common on general liability; ask about auto and umbrella too if your contract requires it there.
4. If you require umbrella or excess coverage, ask whether that policy also follows form and sits over the primary policy for additional insureds.
5. Recheck at every renewal. A new policy year can come with different endorsements.

Related requirements that usually travel together

Primary and noncontributory wording is almost always paired with additional insured status and a waiver of subrogation. If you're asking a sub's agent for one endorsement, ask for all three in the same email. Our free COI request letter generator includes the wording.

Quick checklist

• Contract requires primary and noncontributory coverage for the additional insureds.
• Certificate references it in the description box.
• You have a copy of the endorsement that actually provides it.
• It applies to each line your contract requires (GL at minimum).
• You recheck it when the policy renews.

This guide is general information, not insurance or legal advice. Your contracts, insurance professional, and attorney determine what you should require.